Question

Explain how a protein can be infectious.

Short answer

A protein can be infectious in the form of prions, which are able to induce a misfold in normal proteins, turning them into more infectious material. This process decimates neural tissue, leading to disease and often death.

Step-by-step solution

Introduction to Prions

Prions are proteins that can be infectious. They exist in both a normal form, which is harmless, and an abnormal form, which causes disease. Prions are unique in that they do not contain nucleic acids, unlike bacteria, parasites, fungi, and other pathogenic organisms.

Disease Mechanism

Understanding the disease process begins with normal cell proteins, specifically PrPC. An abnormal form of this protein, known as PrPSc, causes the PrPC proteins to refold into more PrPSc in a domino effect. This replication without DNA or RNA is the trait that makes prions unconventional pathogens.

Misfolding and Aggregation

The misfolded proteins aggregate and accumulate in tissues, particularly in neural tissue. This accumulation leads to devastation of these tissues causing a spongy architecture in the brain, leading to neurodegeneration and, eventually, death.

Infectious Nature

Prions are infectious because they are resistant to procedures that typically inactivate pathogens. This enables them to resist the body's normal defenses and to proliferate in numbers by converting normal cellular proteins to the abnormal form.